1. Field of the Invention
In general, the present invention relates to vibrating separators. In particular, the present invention relates to the design and fabrication of terminal decks typically used with vibrating separators.
2. Prior Art
Many industries utilize vibrating separators to classify certain solid materials by size or to separate solid material from liquid material. In either case, the material is fed to at least one screen surface which retains the oversize particles and allows the smaller particles or the liquid to pass therethrough. A vibrating, shaking or agitating motion is imparted to the screen to effect a more efficient separation and to move the oversize particles on the screen to a discharge area or chute generally located at the periphery of the screen. Specific applications range greatly from food processing to chemical processing to oil field production. In a typical food processing application, a vibrating separator is used to separate various food products according to their size. Vibrating separators used in the food processing industry must be built to exacting industry specifications for sanitation. In chemical processing applications, a vibrating separator can be used to remove particles or debris larger than a preset size from a slurry stream. Vibrating separators are also used in oil production. In oil production, the vibrating separator is typically used to remove larger pieces of debris from recirculated drilling fluids.
The vibrating separators of the prior art are generally constructed of the following major components. A separator blank generally consists of a cylindrical or box-shaped metal structure that is open at the top and bottom ends. Within the separator blank is a screen surface which has tiny openings sized to separate out particles of a particular size while liquids or smaller particles pass through. Located on the peripheral surface of the separator blank is a discharge spout which facilitates the removal of the particles which do not pass through the screen. If the vibrating separator is to be utilized to separate particles of more than one size in a single operation several separator blanks may be stacked on top of each other utilizing successively finer screen sizes. Where several separator blanks are used, the upper separator deck is called the spacing frame or top deck and each successive deck will be called a distribution frame or an intermediate deck. Functionally, without if a larger than normal motion generator, the mass of the decks make more than three or four decks prohibitive.
Located below the separator blank or blanks is a table frame or terminal blank so called because material will not continue through it, but rather will be directed towards the discharge spout on the outside of the blank. The terminal blank generally consists of a cylindrical or box-shaped metal structure constructed in a similar fashion to the separator blank with the exception that instead of a screen, the bottom of the terminal blank is enclosed by a terminal deck plate. The terminal deck plate consists generally of an elliptically-shaped metal sheet which is welded or otherwise secured to the inside of the terminal blank at an angle so as to provide a sloping surface that directs the flow of liquid or solid particles that pass though the screens of the separator deck or decks above to the discharge spout located on the peripheral wall of the terminal blank. The separator blank and terminal blank are attached together by bolts or by some type of fastening, clamping or latching means. Terminal decks come in basically two forms: scalping decks and table frame decks. The scalping deck is designed to allow large volumes of material to flow from the unit quickly. For this reason, it has a sloped surface. A table frame deck consists of a cylindrical body, discharge spout, and domed or convex terminal deck. The convex bottom acts to convey material falling from the screen above to the outside of the deck, then the motion of the machine will propel it toward and out of the spout.
The terminal deck and decks fastened to it are fastened to a motion generating assembly with bolts clamps or other fasteners. The motion generating assembly consists of a motor with eccentric weights fastened to a disk or annulus equal in diameter to the decks.
Vibration of the unit may be achieved by means of an electric, hydraulic, or pneumatic motor. While the vibrating motion of the vibrating separator allows for a great increase in efficiency over non-vibrating separator screens, the constant vibrating motion greatly increases the mechanical stresses on the equipment. The forces experienced can be in the range of 3 to 8 times the force of gravity.
One common result is stress cracks that form in the side of the terminal blank where the discharge spout is welded to the terminal blank. This failure is due to fatigue at the junction of the discharge spout and the terminal blank. The failure is accelerated by localized heat embrittlement of the metal resulting from welding. The terminal deck discharge spouts of the prior art were constructed separately from the blank.
Discharge spouts are generally comprised of three separate pieces of sheet metal cut and bent into shape and then welded together to form the separate terminal deck discharge spout. The discharge spout was then welded on to the outside wall of the deck blank. When the vibrating separator was put into service, the forces exerted on the discharge spout result in metal fatigue and stress cracks in the terminal blank where the weld joints are located.
Another problem present in the vibrating separators of the prior art is the weldjoint that joins the discharge spout to the terminal deck. In order for the vibrating separator to meet industry specifications for food grade equipment which are well known to those of ordinary skill in the prior art, the weld joints joining the discharge spout to the terminal deck must be ground smooth and polished. This extra step of grinding and polishing the weld is labor intensive and adds to the cost of manufacture of the vibrating separator. An example of a vibrating separator of this design is shown by U.S. Pat. No. 3,650,401 which shows a vibrating separator wherein the discharge spout is welded to the peripheral surface of the terminal blank with a joint where the terminal deck butts up against the discharge spout. Solutions offered in the prior art for the failure of terminal deck discharge spouts include gussets and stress relief straps. Others have simply used heavier metal on the deck and spout.
Another attempt to address the problems of the prior art is seen in U.S. Pat. No. 3,794,165 which discloses a terminal deck with a flange extending beyond the peripheral wall of the terminal blank forming a surface which supports the discharge spout but the flange does not actually form part of the spout itself. While the addition of this supporting flange would possibly help to prevent some of the metal stress to the terminal blank, this might increase the strength of the deck at the flange, but would not help the spout failure issue caused by stress where the spout meets the terminal blank. Moreover, the flange does not eliminate the weld joint where the terminal deck butts up against the discharge spout.
Thus, there is a need for a terminal deck assembly which provides greater support for the discharge spout thereby reducing the amount of metal fatigue resulting in greater service life. There is also a need for a terminal deck assembly which minimizes the number of welds which must be ground and polished at great expense of time and labor in order to meet industry specifications for food processing equipment.
In general, the present invention is a new and improved terminal deck assembly for a vibrating separator which is formed from a single piece of sheet metal, such as but limited to, carbon steel, stainless steel, aluminum or another suitable metal. The terminal deck plate of the present invention differs from the prior art in that instead of an elliptical shape the terminal deck plate of the present invention incorporates a tongue which protrudes out through the wall of the terminal blank or container body forming the bottom of the discharge spout. The terminal deck plate of the present invention could also be square or rectangular or any other shape that corresponds to the shape and dimensions of the vibrating separator in which it is used. The terminal deck discharge spout is then fabricated out of two pieces of bent metal which are then welded onto the protruding tongue and the container body. The added support provided by the protruding tongue of the terminal deck plate greatly increases the structural strength of the joint between the discharge spout and the container body and results in increased service life of the equipment. In addition, the terminal deck plate of the present invention eliminates the weld joint between the terminal deck and the discharge spout resulting in labor and cost savings due to the reduction in the number of weld joints which must be ground and polished smooth in order to meet food industry specifications. The protruding tongue of the present invention can be incorporated into both scalping decks and table frame decks.
It is also contemplated that the terminal deck assembly and discharge spout could be constructed of a single sheet of metal with the spout being integral to the terminal deck plate and folded from a single sheet of metal.
In addition, it is contemplated that the terminal deck plate and spout assembly could be formed or molded as a single piece from plastic, a polymer material such as fiberglass, carbon fiber or any other similar material. The terminal deck plate and spout assembly could also be formed integral to the terminal blank assembly as a single piece formed or molded from plastic, a polymer material such as fiberglass, carbon fiber or any other similar material.
It is further contemplated that the vibrating separator of the present invention could be built with multiple stages with different sized separator means, such as but not limited to, screens in order to separate out different sized particles in a single operation.